To add a new category to a page you can click the Category button at the bottom of the page and type in the name you'd like your category to be called.
A full list of existing categories can be found at Special:Categories.
Pages in category "Browse"
“ Hi everyone, Sarah here! Ready for some good news? I've been appointed an Administrator for this...
“ For a full list of help pages, see Help:Contents, which includes help pages shared across Wikia.